Biomedical Engineering Reference
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Fig. 8.65  Comparison of axial velocity profiles for different blood flow behaviour in the symme-
try plane of the sequential anastomosis model. Based on the end of systole for the non-Newtonian
(  continuous line ) and Newtonian (  dashed line ) fluid models, comparison was performed for the
( a ) side-to-side anastomosis and ( b ) end-to-side anastomosis of the sequential anastomosis model.
(Image from Qiao et. al. 2014)
the false lumen after bypass is generally less than that before bypass. The greater the
velocity, the more obvious the reduction. The change is not obvious when the ve-
locity is low, but this does not affect the decreasing trend. Velocity decreases more
significantly in the model with a blind lumen bypassed between the ascending aorta
and the abdominal aorta. For the lumen model, the mass flow ratios of the bypass
graft are 18.7% for bypass between the ascending aorta and abdominal aorta; and
8.4 % for bypass between the left subclavian artery and abdominal aorta. Similarly
for the blind lumen model, the corresponding mass flow ratios are 52.8 and 51.3 %
respectively.
Figure 8.67 shows the distribution of blood pressure at time of 0.04 s where
the values are compared with the reference pressure at the abdominal aorta out-
let. The mean blood pressure on the vessel wall after bypass is generally less than
that without bypass. Peak values of inlet pressure decrease for the lumen models
by 1.09 × 10 3 Pa for the ascending to abdominal aorta bypass, and 6.84 × 10 2 Pa for
the left subclavian artery to abdominal aorta bypass. Similarly peak values of inlet
pressure decrease for the blind lumen models by 3.13 × 10 3 Pa for the ascending to
abdominal aorta bypass, and 2.47 × 10 3 Pa for the left subclavian artery to abdomi-
nal aorta bypass.
8.7.4
Closure
For the coronary artery bypass, flow phenomenon through the coronary arterial by-
pass graft models is characterized by blood flow that deforms structures to an extent
influencing flow patterns through modified geometries. The importance of FSI in
analysing anastomosis models can be emphasized as follows. Distensible vessels
and non-Newtonian rheology influence the haemodynamics of anastomsis models
and improve physiological realism in the simulation. The use of haemodynamic
parameters such as flow patterns, wall deformation, wall shear stress, and time-
averaged wall shear stress can serve as key haemodynamic indicators.
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